Phenol and cyclohexanone are important compounds in the chemical industry and are useful in, for example, the production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, and plasticizers.
Currently, a common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of cumene to the corresponding hydroperoxide, and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone.
Thus, a process that uses higher alkenes instead of propylene as feed and coproduces higher ketones, such as cyclohexanone, rather than acetone may be an attractive alternative route to the production of phenols. There is also a growing demand for cyclohexanone.
It is known from, e.g., U.S. Pat. No. 6,037,513, that cyclohexylbenzene can be produced by contacting benzene with hydrogen in the presence of a bifunctional catalyst comprising a molecular sieve of the MCM-22 type and at least one hydrogenation metal selected from palladium, ruthenium, nickel, cobalt, and mixtures thereof. This reference also discloses that the resultant cyclohexylbenzene can be oxidized to the corresponding hydroperoxide which can then be decomposed to produce phenol and cyclohexanone.
The oxidation of cyclohexylbenzene to produce cyclohexylbenzene hydroperoxide and the cleavage of cyclohexylbenzene hydroperoxide to produce phenol and cyclohexanone are much more complex than the cumene oxidation and cumene hydroperoxide cleavage in the Hock process. For example, the oxidation of cyclohexylbenzene is conducted at low conversion per pass to reduce the formation of undesirable by-products and optimize process yields. The residual cyclohexylbenzene is then typically separated from the cyclohexylbenzene hydroperoxide product and recycled to the oxidation reaction.